1. Technical Field
This disclosure relates to aircraft tail skids in general, and in particular, to a three-position aircraft tail skid mechanism and methods for actuating it.
2. Related Art
A “tail strike” occurs when the tail of a tricycle-gear aircraft strikes the ground during takeoff or landing. Although many tail strikes occur during the “rotation” phase of a takeoff, i.e., a maneuver in which the pilot raises the nose of the aircraft and lowers its tail to achieve a liftoff of the aircraft from the runway, some tail strikes occur during the “flare” phase of a landing, i.e., a maneuver in which the pilot raises the nose of the aircraft and lowers its tail to slow the aircraft and/or decrease its rate of descent toward the runway. Tail strikes are often due to pilot error, as well as to the presence of gusty winds or wind shear.
Tail skids are often provided on tricycle-gear aircraft to prevent or reduce damage to the aircraft in the event of a tail strike. These can range from structures that are fixed to a lower surface of the tail portion of an aircraft's fuselage, to structures that employ a mechanism to move between a deployed position for takeoff or landing operations and a more streamlined, retracted configuration for cruise operation.
Tail skid mechanisms that utilize the same position for takeoff and landing can result in a penalty in that, during a takeoff, they limit downward rotation of the tail to that which is safely allowable for a landing, which may be less than that safely allowable for a takeoff. This results in the use of unnecessarily higher rotation (VR) and liftoff (VLO) speeds during a takeoff, and hence, unnecessarily longer takeoff runs and the need for longer runways.
Accordingly, there is a need for aircraft tail skids that, while effectively preventing or reducing tail strike damage to a host aircraft, can be selectably deployed to and locked in one of three different positions relative to the aircraft, viz., a stowed position, a takeoff position, and a landing position, and that also minimize the number, size and types of the components needed to implement and actuate the mechanism.